by Kevin Johnson and Michael Winter, USA TODAY

by Kevin Johnson and Michael Winter, USA TODAY

The U.S. Capitol Police have launched an investigation into whether an elite tactical team was abruptly recalled from responding to Monday's Navy Yard shooting massacre before D.C. Metropolitan Police officers confronted the shooter.

Two Metropolitan Police officers entered the Navy Yard without the Capitol Police team and one was wounded by the gunman, Aaron Alexis.

Capitol Police spokesman Shennell Antrobus said Wednesday that Chief Kim Dine ordered the independent inquiry, which is to report its findings and recommendations by Oct. 21.

The elite Capitol Police Containment & Emergency Response Team is based just a few blocks from the Navy Yard. A law enforcement source told WUSA-TV the unit was less than 30 seconds from the gate and responded as Metropolitan Police pleaded for help.

A Capitol Police watch commander "wouldn't let them go in and stop people from being slaughtered," one officer told the Washington TV station, which is owned by Gannett, USA TODAY's parent company.

An officer toldThe Washington Post that the officers' union had filed a complaint. The Capitol Police have launched an investigation into the allegation

"We were definitely the closest tactical team in the city," the unidentified officer told the newspaper. "It was at the scene very early on, within a couple of minutes. They were ordered to disengage and turn back. For what reason, we don't know."

Capitol Police acknowledged that the department had "offered and provided mutual support and assistance."

"I take our response to this tragedy and our support to law enforcement partners very seriously," Dine said in a separate statement. "While I am the Chief of Police, at my core I am a police officer who feels strongly about our shared commitment and responsibilities. ... I place a high priority on law enforcement agency relationships and law enforcement coordination and communication."

Dine, a former D.C. district commander , said that he "personally offered assets" to D.C. Chief Cathy Lanier. He also said he was "in close & constant coordination" with D.C. police, the Capitol Police Board, the FBI, Park Police and other responding agencies, "while focused on the security of the Capitol Complex."

The CERT, created in 1978, consists of three "cells" - two assault teams of at least six officers each, plus and a counter-sniper unit. Two teams were on duty Monday and the third was training at Fort Meade, the Post reported.

The Capitol Police say "their primary mission consists of rescuing Congressional members, their staff, and visitors who have been taken hostage by terrorists. Secondary missions include, countering threats made against dignitaries, responding to critical incidents and providing security for major events, such as the Presidential Inauguration."

Congress created the Capitol Police in 1828 to provide security for the Capitol building. Today, the department's duties include protecting members of Congress and their families in addition to policing congressional buildings, parks and streets covering about 25 city blocks.